A. Field of the Invention
The present invention relates to saws used for cutting circular holes through objects made of wood and various other materials, of the type utilizing a cylindrical saw cup coaxially fastened to an arbor holding a pilot drill which protrudes forward of cutting teeth provided on a front annular surface of the saw cup. More particularly the invention relates to a hole saw which automatically ejects a plug sawed from a workpiece, in which hole saw cups of various diameters and having different sized attachment bores may readily be interchangeably mounted on a novel single-ended arbor-holder by a twisting, snapping action.
B. Description of Background Art
In U.S. Pat. Nos. 4,741,651 and 5,096,341, the present inventor disclosed plug ejecting hole saws which utilize a left-hand threaded mandrel or arbor that holds a pilot drill, the shank of which is secured in an enlarged diameter flange or collar located at the front end of the arbor. The arbor is screwed into a threaded, arbor-holder bore disposed coaxially though a bushing or thicker portion of a circular disk-shaped base plate which forms the rear end wall of a cup-shaped saw body which has angled circumferentially spaced apart cutting teeth in the front annular end wall thereof. In a hole saw cup of this type, the front, cup-shaped portion of the saw cup and the thicker rear base plate or arbor-holder bushing are generally fabricated as separate metal parts which are brazed together. Thus, this type of hole saw is sometimes referred to as a xe2x80x9cbi-metalxe2x80x9d hole saw.
A novel feature of the inventions disclosed in the aforementioned patents of the present inventor comprises left-hand threading of both the outer surface of the arbor and the inner threaded bore through the saw cup base. With this arrangement, when the arbor is threaded counterclockwise into the saw cup arbor-holder bore, as viewed from the front of the saw cup and pilot drill end of the arbor, the front flange portion of the arbor advances rearwardly to seat against the inner front wall surface of the saw cup base. The arbor shank, which protrudes rearwardly from the saw cup base is then secured in the collet of a power drill. When the power drill is powered on to turn the pilot drill bit and saw in the usual clockwise cutting direction, as viewed from the rear, shank end of the bit, a counterclockwise reaction torque is exerted on the saw cup teeth by frictional resistance offered by workpiece in response to the cutting action, tending to further tighten and secure the arbor flange against the inner surface of the saw cup base. When the saw cup has penetrated the thickness of a workpiece such as a door panel, a cylindrically-shaped plug of workpiece material becomes lodged tightly within the saw cup, and in prior art hole saws, is difficult to remove from the saw cup. However, in accordance with the ""651 and ""341 patents, a plug lodged within the saw cup may readily be ejected by powering the drill in a reverse, i.e., counterclockwise direction after a hole has been bored through a workpiece, while maintaining the saw cup stationary. Rotating the drill shank and arbor in a counterclockwise direction by the power drill causes the arbor to be advanced axially forward within the threaded bore of the saw cup, and the front flange of the arbor to abut the rear surface of the plug and eject it forward out of the saw cup bore.
The above-described plug ejecting feature of hole saws disclosed in the present inventor""s ""651 and ""341 patents has provided a highly effective and widely accepted improvement in bimetal hole saws. Subsequent to issuance of those two patents, U.S. Pat. No. 5,435,672 was issued for adapters having a left-hand threaded arbor-receiving bore, and a right-hand external bore. The adapters were designed to be threaded into right-hand threaded arbor-holder bores of existing saw cups, thus accommodating left-hand threaded arbors and permitting the present inventor""s novel plug ejecting function to be accomplished using existing hole saw cups having right-hand threaded arbor-holder bores.
Although the novel plug ejecting hole saws disclosed in the present inventor""s ""651 and ""341 patents constituted a substantial advancement in the art for hole saws having a base provided with a threaded bore for receiving an arbor, there is another type of widely employed hole saw cup which formerly could not utilize the advantageous plug ejecting construction disclosed in those patents. This type of hole saw is sometimes referred to as a xe2x80x9cCarbonxe2x80x9d type, since it uses hole saw cups fabricated as a unitary structure, e.g., a deep drawn cup, made from high carbon steel. In this type of hole saw, the saw cup base is made of relatively thin stock, thus precluding the use of threaded bore through the base as a means for attaching the saw cup to an arbor. Instead, hole saws with thin base walls are typically provided with a non-circular, e.g., a double-D-shaped central bore through the base, which receives the complementary-shaped, enlarged rear portion of an arbor which is secured to the base by a threaded fastening member.
In response to a need for a plug ejecting hole saw which may utilize thin base wall, non-threaded saw cups of the type described above, the present inventor developed a plug ejecting hole saw which utilizes thin base wall, non-threaded saw cups having an oblong or xe2x80x9cdouble Dxe2x80x9d-shaped attachment bore. That device, described in U.S. Pat. No. 6,341,925, Plug Ejecting Hole Saw With Twist-Locking Interchangeable Saw Cups, includes an arbor holder comprising a slotted cylindrical body coaxially held in spring biased, longitudinally slidable disposition within a collar. The slotted cylindrical body has a pair of longitudinally disposed, diametrically opposed grooves formed in opposed flats formed in a nose piece portion of the cylindrical body which protrudes forward from the collar. Each longitudinal groove longitudinally slidably holds a locking tab which is spring biased forwardly to an outward position to thereby block an adjacent one of a pair of circumferential grooves formed in two curved portions of the nose piece located between the two flats. The locking tabs are pushed axially rearward against the spring force by a saw cup base to unblock the circumferential grooves, enabling peripheral edge wall surfaces of the saw cup bore to be rotated into the circumferential grooves, thereby preventing relative longitudinal movement between the saw cup and the arbor holder. When the saw cup has been rotated sufficiently far, the locking tabs spring forward into the larger radius, curved portions of the saw cup attachment bore to thereby lock the arbor holder to the saw cup for both clockwise and counterclockwise rotations.
An embodiment of the device disclosed in the ""925 patent includes a second, rear nose piece protruding from the cylindrical body at the opposite longitudinal end from the front nose piece, the rear nose piece being of a different size to fit saw cups having a different size attachment bore than the front nose piece, a second spring bias means, a second pair of locking tabs, and frictional means to position the cylindrical body and nose piece portions axially centered within the collar. The present invention was conceived of to provide a plug ejecting hole saw which utilizes a novel single-ended arbor holder that is interchangeably and bi-directionally lockable to saw cups having at least two different sized attachment bores.
An object of the present invention is to provide a plug ejecting hole saw including an arbor-holder which can be attached to hole saw cups of various body diameters and attachment bore sizes.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder which can be secured to the base of a hole saw cup with non-threaded fastening means including a single spring-loaded locking tab.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder which utilizes a single spring-loaded locking tab to removably secure the arbor holder to the base of a non-threaded hole saw cup having an unthreaded attachment bore through the base of the hole saw cup for attaching to an arbor, the arbor-holder having therethrough an axially disposed left-hand threaded bore for threadingly receiving an arbor.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder which is removably securable to a hole saw cup provided with a non-circular attachment bore through its base, the arbor-holder having a front nose piece boss insertable forward through the attachment bore, the boss having formed in curved wall surfaces thereof a pair of spaced apart circumferential grooves which rotatably receive peripheral edge walls of the saw cup attachment bore to prevent relative longitudinal motion between the saw cup and arbor holder, and a locking tab which springs forward to lock the arbor-holder against disengagement from the saw cup when the arbor-holder is rotated clockwise and counterclockwise with respect to the saw cup base.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder having an outer collar and inner body disposed axially therethrough, the inner body having a lefthand threaded bore disposed axially therethrough for receiving an arbor, a front nose piece having a boss which slidably holds a locking tab which releasably blocks a first circumferential groove which cooperates with a second circumferentially spaced apart groove to lockingly engage the base of a hole saw cup when the front nose piece boss has been inserted into and rotated in a first direction within an attachment bore provided through the base of saw cup, the locking tab and groove being released from locking engagement with the saw cup base when the collar of the arbor-holder is pulled axially rearward with respect to the inner body thereof to thereby retract the locking tab, and rotated in the opposite direction.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder having an outer collar which axially slidably holds an inner body having disposed axially therethrough a left-hand thread for receiving an arbor, the inner body having a nose piece provided with a first, front, nose piece boss lockingly engageable and releasable within a first size attachment bore through a selected one of a first plurality of hole saw cups, and a second, larger nose piece boss rearward of the front boss releasably engageable within a second, larger sized attachment bore through a selected one of a second plurality of hole saw cups.
Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims.
It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, I do not intend that the scope of my exclusive rights and privileges in the invention be limited to details of the embodiments described. I do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims.
Briefly stated, the present invention comprehends a plug-ejecting hole saw device for use with power drills. The device includes an arbor holder which has a left-hand threaded bore that threadingly receives an arbor which includes a front pilot drill and a rear shank which is clamped into the chuck of a power drill, and a saw cup which is attached to the arbor holder, coaxially over the arbor. When the power drill is operated in a reverse, i.e., counterclockwise sense, the arbor advances threadingly in the arbor holder to automatically eject a cylindrically-shaped plug produced in cutting a hole through an object by the drill powered in a clockwise sense.
A plug ejecting hole saw according to the present invention includes an arbor-holder removably attachable to a hole saw cup selected from a plurality of hole saw cups of various sizes. A main embodiment of a plug ejecting hole saw according to the present invention includes an arbor-holder removably attachable to a selected hole saw cup of the type having a cylindrical cup-shaped body provided with angled cutting teeth protruding from the front annular surface of the body, and a relatively thin rear circular base wall having through its thickness dimension a non-circular attachment bore for attachment to an arbor concentrically aligned with the front annular surface of the body, A preferred arbor attachment bore for saw cups according to the present invention has a xe2x80x9cdouble-Dxe2x80x9d shaped perimeter formed from diametrically opposed arc segments of a circle which is concentric with the circular hole saw cup face, the circle being truncated on opposite sides thereof by a pair of chords equidistant from and parallel to a diameter which perpendicularly bisects the arcs. Thus, a preferred arbor attachment bore provided through the base of a saw cup according to the present invention has an inner peripheral edge wall consisting of a pair of diametrically opposed laterally symmetric circular arc segments centered at 90-degree and 270-degree locations of a circle, and two diametrically opposed flat segments centered on zero-degree and 180-degree locations of the circle.
A main embodiment of an arbor-holder for use with hole saw cups of the type having a double-D-shaped arbor-holder attachment bore through the base of the saw cup includes an outer cylindrical housing or collar having therethrough a circular bore which axially slidably holds a body having cylindrical outer wall surfaces which fit within the collar bore. The cylindrical body has a nose piece which protrudes axially outwardly of the front annular surface of the collar, the nose piece having a longitudinally or axially disposed front boss that has an outer transverse cross-sectional shape similar to that of a double-D-shaped arbor-holder attachment bore through a saw cup base, but has a slightly smaller size permitting ready insertion of the nose piece boss into the attachment bore.
The nose piece boss has protruding radially inwards from opposed cylindrical wall surfaces thereof a pair of transversely disposed grooves. Each groove has in a transverse sectional view the shape of a circular arc segment and protrudes radially inwardly into a separate one of two longitudinally disposed curved side walls of the nose piece. Also, each of the grooves has a transverse front or outer edge wall located rearwardly of and parallel to the outer front face of the front nose piece boss, forming between the front groove edge wall and the front nose piece face an annular arc-shaped front flange. A rear transverse edge wall of each of the two transversely disposed grooves is defined by a front transversely disposed annular wall surface of a rear portion of the nose piece.
Each of the two transverse nose-piece boss grooves is disposed circumferentially from a location circumferentially spaced apart from a junction between a flat and curved side of the double-D-shaped nose piece, the junctions comprising a pair of diagonally opposed, longitudinally disposed shoulder ribs, which are disposed rearwardly from the front transverse face of the nose piece boss to the front or outer transversely disposed annular wall surface of a larger diameter rear portion of the nose piece. The nose piece boss also has a pair of parallel, upper and lower laterally disposed flats spaced equal distances from the center of the boss. One of the flats, e.g., the upper flat, has formed therein a rectangularly-shaped longitudinal groove which is disposed rearwardly from the longitudinally front or outer transverse edge wall of a transverse groove.
The longitudinal groove is laterally centered on a longitudinal plane which bisects the two diametrically opposed flats of the nose piece. Also, the longitudinal groove is disposed rearwardly or axially inwardly through an adjacent arc-shaped transverse groove and extends longitudinally rearward through the inner cylindrical body to a location forward of the rear transverse wall surface of the inner cylindrical body, and penetrates the outer cylindrical wall surface of the inner cylindrical body. The longitudinal groove longitudinally slidably receives a step-shaped locking tab support lug having a xe2x80x9cfront stepxe2x80x9d portion which functions as a front locking tab that has a longitudinal thickness approximating that of the transverse groove in the nose piece, and a radial thickness slightly less than that of the radial depth of the longitudinal groove. The lug also has a rear block portion of greater radial thickness than the front locking tab, which is slidably received within that portion of a longitudinal groove located within the inner cylindrical body. The rear portion of the lug is urged axially forward by spring means, e.g., a helical compression spring, and is limited in forward axial movement by contact of a rearwardly protruding retainer pin attached to the upper surface of the top step portion of the lug and slidably received within a threaded blind bore axially disposed within the collar, with an end wall of the bore.
When the inner cylindrical body of the arbor-holder is pushed axially forward or outwardly from the collar against the resilient force provided by the compression spring, the nose piece is displaced forward or axially outwardly of the front annular face of the collar. This displacement causes the front shoulder edges of the longitudinal locking tab groove to move forward of the front transverse edge wall of the locking tab. With the cylindrical inner body pushed sufficiently far forward within the collar, the rear transverse edge wall of the transversely disposed groove is moved axially outwards or forward of the front edge of the tab, unblocking the junction or passageway between the transverse groove and the longitudinal tab groove adjacent to it. Also, when the nose piece is inserted forward into the arbor-holder attachment bore of a hole saw cup, contact of the rear surface of the saw cup with the front vertical surface of the locking tab pushes the locking tab rearwardly within its longitudinal groove against a resistance force provided by the compression spring. Rearward motion of the locking tab unblocks the transverse groove, thus allowing an adjacent portion of the peripheral attachment bore edge wall to be rotatably received within an adjacent transverse groove of the nose piece boss, and a diagonally opposite transverse groove not provided with a locking tab to receive a diagonally opposite portion of a peripheral attachment bore edge wall, and thereby allowing the entire arbor assembly to be rotated clockwise with respect to the hole saw cup. When the rotation angle approximates forty-five degrees, the locking tab springs axially forward in response to a spring extension force exerted by the compression spring, into a radial clearance space formed between the nose piece flat holding the tab, and an adjacent curved inner peripheral edge wall of the saw cup attachment bore. In this disposition, the curved portions of the nose piece boss, which have outer longitudinal surfaces spaced farther apart than the flats of the peripheral wall adjacent the attachment bore through the saw cup base, are axially aligned with the peripheral wall flats. Thus, the peripheral wall flats are retained axially within the transverse nose piece grooves in this position. Further clockwise rotation of the arbor-holder with respect to the saw cup base is limited by contact of a longitudinally disposed nose piece rib with an intersection between the curved and flat portions of the peripheral edge wall of the hole saw cup attachment bore. Counterclockwise rotation of the arbor-holder relative to the saw cup is limited by contact of a longitudinal edge of the locking tab with an intersection between a curved and flat edge wall of the saw cup attachment bore. With this arrangement, the saw cup is locked axially and rotationally to the arbor-holder.
The inner cylindrical body of the arbor-holder according to the present invention has through its thickness dimension a longitudinally disposed bore coaxial with the arbor-holder collar. The bore has internal left-hand threads adapted to receive an arbor threaded into the bore through a front opening thereto in the front or outer face of the nose piece, either before or after the arbor-holder has been snap-locked into a saw cup as described above.
The arbor is provided with a shank which protrudes rearwardly from the rear surface of the arbor-holder. A collet flange at the front end of the arbor-holder holds a pilot drill, and the rear face of the collet flange seats against the front face of the arbor-holder nose piece, when the arbor is threadingly tightened in the arbor-holder bore in a counterclockwise sense, as viewed from the front of the pilot drill. To use the hole saw, the rearwardly protruding shank of the arbor is clamped in the chuck of a power drill. Then, the tip of the pilot drill is placed in perpendicular contact with a workpiece, and the drill is then powered on to rotate the hole saw in a clockwise sense as viewed from the shank end of the hole saw, thereby cutting a circular hole through a workpiece and leaving a cylindrically-shaped plug of workpiece material lodged within the hole saw cup. The drill is then angled slightly away from the orientation perpendicular to the workpiece used to bore the hole, thus slightly cocking the hole saw cup within the hole cut through the workpiece, and thereby frictionally lodging the hole saw cup within the workpiece hole. The power drill is then powered on in a reverse sense to rotate the arbor in a reverse sense, thus causing the arbor and flange to be threadingly advanced within the arbor-holder bore, thereby ejecting the workpiece plug forwardly out from the saw cup body.
When it is desired to remove the arbor-holder from a saw cup body, e.g., to install the arbor-holder and arbor in a different saw cup body, which may be of a different size, the collar of the arbor-holder is pulled rearwardly with respect to the front nose piece and saw cup body, thus retracting the locking tab in the longitudinal nose piece groove to thereby unblock the adjacent transverse groove and adjacent curved peripheral wall of the saw cup attachment bore. With the locking tab thus disengaged from the hole saw cup, the arbor-holder is rotated counterclockwise to align the flats and curves of the nose piece boss once again with the correspondingly shaped edge walls of the saw cup attachment bore, thus allowing the nose piece and entire arbor-holder to be pulled rearwardly and disengaged from the saw cup body.
In a preferred embodiment of a plug ejecting hole saw device according to the present invention, the nose piece of the cylindrical body is provided with a second, longitudinally intermediately located double-D-shaped boss rearward of the front boss, the second boss being coaxially aligned with the front boss, but having a larger diameter for use with larger saw cups having a larger attachment bore. The rear nose piece boss is identical in shape and function to the front nose piece boss. However, in this embodiment, the locking tab lug has a second, intermediate step located between a front step and a rear block portion of the lug. Thus, as in the single boss embodiment, the locking tab lug for the double boss arbor holder has a first, front locking tab consisting of a front step portion which has a radial thickness slightly less than that of the radial depth of the longitudinal tab groove which penetrates the transverse upper groove of the front nose piece boss. This reduced radial height or thickness provides clearance for the flat peripheral edge wall of a larger diameter attachment bore through a larger hole saw cup, the clearance enabling the saw cup to be pushed rearward of the front nose piece, to fit conformally over a larger diameter, rear boss. When the periphery of the larger diameter attachment bore is axially aligned with the rear boss, and pushed rearward, the rear wall surface of the saw cup presses against a front vertical surface of the second, intermediate step, which is intermediate in height between the front step and the rear block portion of the lug. The intermediate, or second, step which may have a radial thickness slightly greater than the rear portion of the longitudinal groove which penetrates the rear transverse groove, comprises a second, rear locking tab which is lockingly engaged and disengaged with the attachment bore of a larger diameter saw cup in the exact same manner as described above for the front nose piece boss.